When I start a new audio track it asks me which input (1 or two) I want to use, but how do I change it once it's made? Can't figure out how to get back to that window.

Hi Allen - You can select/change the particular input on the current Input Device (interface) in the Smart Controls panel: - Select the Audio track and hit shortcut "B" to open the Smart Controls panel at the bottom (if it's not already open) - Under the Recording Settings tab, select/change the particular input in the Input menu If necessary you can change the interface in GarageBand menu > Preferences... > Audio/MIDI > Input Device